U.S. patent number 4,026,685 [Application Number 05/641,248] was granted by the patent office on 1977-05-31 for flow reversing regenerative air dryer.
This patent grant is currently assigned to Wagner Electric Corporation. Invention is credited to Arthur R. Grix.
United States Patent |
4,026,685 |
Grix |
May 31, 1977 |
**Please see images for:
( Certificate of Correction ) ** |
Flow reversing regenerative air dryer
Abstract
A flow-reversing, regenerative, desiccant air dryer system
absorbs moisture, oil droplets, and carbon particles from the
incoming air during compression in a compressed air system. Once
sufficient air pressure has been attained in an air pressure
reservoir, control valves direct the flow of atmospheric-pressure
air, heated by passing through the warm compressor cylinder, in a
reverse direction through the air dryer. The reverse flow of
heated, atmospheric pressure air both purges the trapped oil,
carbon particles, and condensed liquid water and removes the
moisture from the desiccant.
Inventors: |
Grix; Arthur R. (St. Louis
County, MO) |
Assignee: |
Wagner Electric Corporation
(Parsippany, NJ)
|
Family
ID: |
24571586 |
Appl.
No.: |
05/641,248 |
Filed: |
December 16, 1975 |
Current U.S.
Class: |
96/113; 55/302;
55/337; 96/400; 96/137; 55/283; 137/204 |
Current CPC
Class: |
B01D
46/30 (20130101); B01D 53/0446 (20130101); B01D
53/0454 (20130101); B01D 53/26 (20130101); B01D
53/0431 (20130101); B01D 2257/80 (20130101); B01D
2259/4009 (20130101); Y10T 137/3105 (20150401) |
Current International
Class: |
B01D
46/30 (20060101); B01D 53/04 (20060101); B01D
53/26 (20060101); B01D 046/00 () |
Field of
Search: |
;55/212,213,215,216,218,267-269,316,303,302,59,62,163,387,388,389,DIG.17,283
;137/204 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Nozick; Bernard
Attorney, Agent or Firm: Eyre, Mann, Lucas & Just
Claims
What is claimed is:
1. In an air compressor system of the type wherein an air
compressor delivers compressed air through an air dryer to an air
pressure reservoir, the reversible-flow regenerative drying system
which comprises:
(a) a pressure container;
(b) said pressure container having a compressed air inlet, a
compressed air outlet, a purge air inlet and a purge air
outlet;
(c) an inner container having sorbent material therein within said
pressure container, said inner container being substantially
coaxial to and spaced from said pressure container whereby an air
space is provided therebetween;
(d) means for sealing one end of said inner container to said
pressure container intermediate said compressed air inlet and
outlet;
(e) the ends of said inner container having means for allowing the
passage of air therethrough;
(f) the purge air inlet adjacent to said compressed outlet;
(g) said purge air outlet being at the end remote from said purge
air inlet whereby purge air is enabled to flow through said sorbent
material in a direction the reverse of the flow of the compressed
air;
(h) valve means for opening said purge air outlet; and
(i) a unidirectional valve interposed between said compressed air
outlet and said air pressure reservoir.
2. A drying system as recited in claim 1 wherein said sorbent
material further comprises:
(a) first fibrous filter means on the upstream side of said inner
container adapted to removing oil droplets and solid contaminant
particles from said compressed air stream;
(b) a container of desiccant material located in said inner
container downstream from said first fibrous filter means, said
desiccant material being adapted to sorption of water vapor from
said air stream; and
(c) second fibrous filter means on the outlet side of said inner
container downstream from said desiccant material, said second
fibrous filter means being adapted to removing oil droplets and
solid contaminants from the purging air stream before it reaches
said desiccant material.
3. A drying system as recited in claim 1 further comprising:
(a) means for sensing the pressure in said air pressure
reservoir;
(b) a pressure governor adapted to producing a control pressure
signal when said sensed pressure exceeds a first level and further
adapted to removing said control pressure signal when the sensed
pressure drops to a second, lower pressure level; and
(c) said valve means being adapted to connecting the stream of air
from said compressor to said compressed air inlet through said
absorbing means and thence through said compressed air outlet into
said pressure reservoir during the absence of said control pressure
signal and further adapted to connecting the stream of air from
said compressor to said purge air inlet and opening said purge air
outlet during the presence of said control pressure signal.
4. In a compressed air system of the type wherein an air compressor
delivers compressed air through an air dryer to an air pressure
reservoir, the reversible-flow regenerative dryer comprising:
(a) inner and outer containers;
(b) annular sealing means between said inner and outer
containers;
(c) air passage means below said sealing means between said inner
and outer containers;
(d) heat exchanger means defining the exterior surface of said
outer container adjacent to said air passage means;
(e) tangential air inlet means adapted to directing the flow of
incoming air in a tangential direction into said air passage
means;
(f) a sump at the bottom of said outer container in which liquid
water, which has been condensed from the air stream, may collect
during air compression;
(g) first and second fibrous filters inside perforated upper and
lower ends respectively of said inner container;
(h) desiccant material filling at least a portion of the volume of
said inner container between said first and second fibrous
filters;
(i) a compressed air outlet and a purge air inlet in the top of
said outer container above said sealing means;
(j) a purge valve below said sump, said purge valve being adapted
to venting air, liquid water, particulates, oil, and water vapor
from the inside of said outer container to the atmosphere when
opened;
(k) a control valve, mechanically connected to said purge valve,
said control valve being adapted to opening said purge valve upon
receipt therein of a pressure control signal;
(l) valve means for disconnecting the compressed air from said air
compressor to said tangential air inlet and connecting it to said
purge air inlet and opening said purge valve upon the attainment of
a predetermined air pressure in said air pressure reservoir;
and
(m) a unidirectional valve between said compressed air outlet and
said air pressure reservoir.
5. A drying system as recited in claim 1 further comprising:
(a) the axis of said compressed air inlet being substantially
tangential to said air space; and
(b) said compressed air inlet being on the side of said means for
sealing remote from said compressed air outlet whereby said
compressed air injected into said air space travels in a spiral
path along a substantial length of said air space.
Description
BACKGROUND OF THE INVENTION
A system that compresses air compresses all of the gases and vapors
that exist in the air that enter the system. Immediately following
the compression function the gases and vapors are still in their
gaseous state as a result of the high temperatures from the almost
adiabatic compression process. However, due to the subsequent
transfer of the heat of compression to the outside air, the
temperature of the compressed air in the system rapidly approaches
ambient air temperature. Water vapor, one of the constituents of
air, undergoes a phase transformation at a temperature between the
compression temperature and ambient air temperature. The air in the
system becomes saturated with water vapor and liquid water
condenses.
Water in the liquid state has a detrimental affect on an air
compressor system. Water washes away lubricants and, when the
ambient temperature drops below the freezing point, water freezes
in the system causing equipment stoppage, possible malfunction and
danger.
Desiccant air dryers have been used to remove liquid water and
water vapor from compressed air systems. Desiccant materials,
however, eventually become saturated and stop absorbing water
vapor. Several methods have been employed to regenerate saturated
desiccants so that they may be reused. In one method, the system is
shut down while water-saturated desiccant is removed and dried by
heating. In other systems, two desiccant containers are alternately
on-line between the compressor and the pressure reservoir. Each
desiccant container is provided with a heating source. The
desiccant container which is off-line at any particular time is
opened to the atmosphere and heated to drive off the trapped
moisture. Refinements of this method use a small amount of the
dried outflow from the on-line cylinder to help dry the desiccant
in the off-line cylinder.
Although the preceding methods are known to work, they are
inconvenient and costly to install and to operate. In addition,
they make inadequate provision for disposing of oil particles and
burned carbon particles which normally pass from the compressor in
the air stream. The oil particles, if not removed, poison the
desiccant material.
SUMMARY OF THE INVENTION
During the compression cycle, the present invention directs the
flow of compressed, water-saturated air, also containing oil
droplets and carbon particles into a sealed air dryer. Within the
air dryer, the air flows in a spiral laminar sheet between an outer
heat-exchanger surface and an inner cylindrical cartridge. The
cylindrical cartridge has a perforated plate at each of its ends. A
layer of fibrous filter material inside the perforated plate at
each end excludes oil droplets and carbon particles. Adsorbent
desiccant material fills the cylindrical container between the two
fibrous filters. The air passes through the bottom perforated plate
into the bottom of the cylindrical desiccant cartridge, depositing
its contained oil droplets and carbon particles in the fibrous
filter and giving up its water to the desiccant. The dried air
flows out the top of the sealed container, through a unidirectional
valve into a pressure reservoir.
When the pressure in the pressure reservoir attains a predetermined
threshold level, control valves redirect the flow of air from the
compressor to begin the drying cycle. A purge valve in the bottom
of the dryer is fully opened to the atmosphere. The pressure stored
in the dryer and in the lines upstream of the unidirectional valve
is explosively vented through the purge valve to the atmosphere
carrying with it the liquid condensed water from a sump in the
bottom of the container and the trapped oil droplets and carbon
particles from the bottom fibrous filter. The compressor outflow
line is switched to a top fitting adjacent to the outlet fitting
which normally feeds the pressure reservoir during compression. The
compressor begins to pump atmospheric-pressure air in the reverse
direction downward through the top perforated plate of the
desiccant container, through the desiccant and through the purge
valve to the atmosphere. The fibrous filter in the top of the
dessicant container traps oil droplets and carbon particles during
this operation. The compressor body becomes heated during the
compression cycle. The atmospheric pressure air is heated in its
passage through the compressor on its way to passing through the
desiccant material. The heated, atmospheric pressure air carries
off the moisture trapped in the desiccant material, preparing it
for the next compression cycle.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a schematic diagram of an air compressor system
illustrating an embodiment of this invention during the compression
cycle.
FIG. 2 shows a schematic of the same air compressor system during
purging according to the teachings of this invention.
FIG. 3 shows a cross-sectional view of the dryer.
FIG. 4 shows a cross-sectional view of the dryer along 4--4 in FIG.
3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The following description, written with reference to FIG. 1,
details the operation of the system during the compression cycle.
The compressor 10 provides pressurized air through the compression
outlet 12 of an unloader valve 14. The heated compressed air flows,
as indicated by the arrows, along a pressure pipe 16, into a
pressure inlet 18 in the sealed pressure vessel 20. As shown by the
arrows, the incoming air spirals downward in a sheet around the
inside of the pressure vessel 20. The exterior of the pressure
vessel 20 may be fitted with convection-cooling fins 70 to improve
the transfer of heat from the sheet of heated compressed air to the
ambient air. As the compressed air gives up heat, moisture
condenses on the inner surface of the pressure vessel and collects
in a sump (24 see FIG. 3) at the bottom of the pressure vessel 20.
The cooled air, still saturated with water vapor and containing
other contaminants, begins to travel upward toward the center
outlet 26 in the pressure cap 28 of the pressure vessel 20. The
manner of filtering and drying the air will be described later.
The dry air emerging from the top of the pressure vessel 20 is
carried by a discharge line 30, through a unidirectional valve 32,
and into an air pressure reservoir 34. An air pressure reservoir
outlet 36 feeds compressed air through a demand line 38 to the
using equipment. A pressure relief fitting 40 and pressure relief
line 42 feed a sample of the pressure in the reservoir 34 to a
pressure relief valve 44. A pressure sensing line 46 feeds a sample
of the pressure in the pressure relief line 42 to a pressure
governor 48. When the pressure reaches a predetermined value, the
pressure governor 48 connects a pressure control signal on control
line 50 to the unloader valve 14 and to a purge valve 52 located at
the bottom of the pressure vessel 20. The control signal opens
purge valve 52 providing direct access to the atmosphere from the
bottom of the pressure vessel 20. This allows trapped liquid water,
oil droplets and burned carbon particles to exhaust into the
atmosphere. This venting process is aided by the discharge of
pressure from the pressure vessel 20 pressure pipe 16, and the
portion of the discharge line 30 upstream of the unidirectional
valve 32. The unidirectional valve 32 prevents discharge of the
pressure stored in the reservoir 34.
The control signal also causes the unloader valve 14 to close
compression outlet 12 and connect purge outlet 54 to the compressor
10 output. This change in valve conditions sets up the flow during
purge shown in FIG. 2. The compressor 10 continues to run during
the purge operation. Air is pumped through purge line 56 into a
purge fitting 58 in the pressure cap 28. As indicated by the
arrows, purge air, at approximately atmospheric pressure, flows
downward through the pressure vessel 20 and out the purge valve 52
at the bottom. The drying process is aided by the fact that the
compressor 10, heated during the compression part of the cycle,
contributes heat to the incoming air stream.
When the air pressure in the reservoir 34 decreases to a
predetermined value, the pressure governor 48, sensing this
condition removes the pressure control signal from the control line
50. This change causes the unloader valve 14 and the purge valve 52
to resume their conditions for a new compression cycle as described
in connection with FIG. 1. The system continues to alternate
between compression and purge cycles.
Referring now to the detailed cross-sectional drawing of the
pressure vessel 20 shown in FIG. 3, the pressure vessel 20 consists
of a lower shell 60 and a pressure cap 28. An outward-directed
flange 62 at the upper end of the lower shell 60 mates with a
cooperating outward flange 64 on the lower end of the pressure cap
28. A resilient gasket 66, fitting in an annular groove 68 in the
flange 62 provides a pressure-tight seal between the lower shell 60
and the pressure cap 28. A retaining ring 67, of a type well known
in the art, clamps the two flanges 62, 64 together. At least a
portion of the lower shell 60 is preferably provided with
convection-cooling fins 70 on its outer surface. The pressure inlet
18 is located on the upper side of the lower shell 60. The axis of
the pressure inlet 18 is tangential to the lower shell 60. Thus
entering air is directed in a counter-clockwise spiral (as seen
from above) about the inside of the lower shell 60.
A desiccant container, consisting of a lower part 72 and a cap 74
is fitted inside the lower shell 60. An annular enlargement 76 at
the top of the lower portion 72 fits snugly within the lower shell
60. Below the annular enlargement 76, the slightly narrower profile
of the lower part 72 leaves an annular cylindrical air space 78.
The bottom of the desiccant container 80 rests on four support bars
82. Referring momentarily to the cross-sectional view in FIG. 4,
the four support bars 82 are arranged in an x with a central
opening 84. The space between the bars 82 plus the central opening
84 define a sump 24 into which condensed liquid water and oil
droplets may drain.
Returning now to FIG. 3, the bottom of the desiccant container 80
is perforated with a plurality of openings 88. Inside the bottom
80, a lower fibrous filter 90 is situated between the bottom 80 and
a perforated retainer plate 92. A conical spiral spring 94 applies
axial pressure between the perforated retainer plate 92 and a lower
perforated desiccant retainer plate 96. The openings in the lower
perforated desiccant retainer plate 96 are smaller than the
desiccant particles. The central region of the desiccant container
98 contains granular adsorbent desiccant material.
At its upper end, the inner diameter of the lower part 72 of the
desiccant container is increased. The annular ridge 100 thus formed
provides a mounting surface for an upper perforated desiccant
retainer plate 102. The inside of the increased inner diameter
contains inside threads 104. Mating outside threads 104a on the lip
106 of the cap 74 secures together the cap 74 and the lower part 72
of the desiccant container. The inner shoulder of the lip 108
presses the upper desiccant retainer plate 102 against the annular
ridge 100. A resilient O-ring 110 is compressed between the upper
lip of the lower part 112 and a cooperating lip on the cap 114. As
the cap 74 is screwed into the lower part 72, the O-ring 110 is
compressed between the surfaces. This not only provides an air- and
moisture-tight seal between the cap 74 and lower part 72 of the
desiccant container, but also causes the O-ring 110 to protrude
outward whereby an air- and moisture-tight seal is also produced
between the desiccant container and the lower shell 60 of the
pressure vessel 20. This latter seal ensures that the only possible
communication between the lower part of the pressure vessel 20 and
the pressure cap 28 must be accomplished through the desiccant
container. An upper fibrous filter 116 occupies the space between
the upper desiccant retainer plate 102 and the top of the cap 118.
The top of the cap 118 is pierced with a plurality of openings 120
to enable the passage of air.
A helical spring 122 applies axial pressure between the pressure
cap 28 and the cap 74 of the desiccant container to retain the
desiccant container in position against the upward force of the
incoming air.
The purge valve 52 shown at the bottom of the lower shell contains
a purge cylinder 123 and a control cylinder 124. A purge piston 126
and a control piston 128 are mechanically connected together by an
axial rod 130. A helical return spring 132 of negligible force
urges the purge piston 126 against its seat 134. Resilient material
136 on the mating face of the purge piston 126 provides an air- and
moisture-tight seal when the purge piston 126 is in its closed
position as shown. A threaded plug 138 seals the outer end of the
purge cylinder 123 and provides a bearing surface 140 against which
the helical return spring 132 presses. A drain hole 142 provides
drainage for water and other contaminants between the sump 24 and
the purge cylinder 123.
A resilient annular control-piston gasket 144 provides an air-tight
seal between the control piston 128 and the control cylinder
124.
The hole 146 in the seat 134 of the purge cylinder 123 is
considerably larger in diameter than the axial rod 130 which passes
through it. Thus, when the purge valve 52 is opened there is
adequate space for air and contaminants to pass from the purge
cylinder 123, through the hole 146, into an outer chamber 148 and
thence through an exhaust port 150 to the atmosphere.
OPERATION
During compression, heated, compressed, moisture-laden air, also
containing oil droplets and burned carbon particles enters the
pressure container 20 tangentially through pressure inlet 18.
Prevented from going upward by the seal provided by the resilient
O-ring 110, the incoming air is forced to spiral downward in a
sheet between the inner surface of the lower shell 60 of the
pressure vessel 20 and the outer surface of the lower part 72 of
the desiccant container. In its travel toward the bottom, the air
gives up much of its heat of compression to the walls of the lower
shell 60 which are kept cool by the convection-cooling fins 70. As
it gives up its heat, the air becomes saturated with moisture and
deposits the excess moisture on the inner surface of the lower
shell 60. This moisture drains into the sump 24. When it reaches
the bottom, the cooled but still water-saturated air enters the
desiccant container through the openings 88 in the bottom. The
lower fibrous filter 90 removes oil droplets and carbon particles
from the air stream. The air thereupon passes upward through the
openings in the perforated retainer plate 92 and the lower
perforated desiccant retainer plate 96 and into the desiccant
material in the central region 98. As it passes through the
desiccant material the air gives up its water vapor to the
desiccant. The dried air then passes through the openings in the
upper desiccant retainer plate 102, the upper fibrous filter 116,
and cap 74 into the pressure cap 28. The dried compressed air
passes through the center outlet 26 to the reservoir. The purge
fitting 58 is blocked by the unloader valve 14 (see FIG. 1) at this
time.
When a preset value of air pressure is attained in the reservoir, a
positive control pressure is connected through the control pipe 50
to the control cylinder 124. The positive control pressure in the
control cylinder 124 forces the control piston 128 toward the
right. The purge piston 126 is moved out of engagement with its
seat 134. The pressure stored in the pressure vessel 20 is
explosively vented through the exhaust port 150 carrying with it
all water and oil trapped in the sump 24. In addition, the
explosive release of pressure tends to expel oil and carbon
particles trapped in the lower fibrous filter 90.
The compressor output at this time is connected to the purge
fitting 58; the center outlet 26 and the pressure inlet 18 being
blocked. Heated, atmospheric-pressure air is pumped from the
compressor through the purge fitting 58 and the desiccant in the
central region of the desiccant container 98, thence out the purge
valve 52 to the atmosphere. The flow of atmospheric-pressure air
carries off the trapped moisture, drying the desiccant in
preparation for the next compression cycle.
At the end of the purge cycle, the positive control pressure
through the control pipe 50 is released. The helical return spring
132 urges the purge piston 126 into engagement with its seal 134.
The purge fitting 58 again becomes blocked, and the compressor air
flow is again directed into the pressure inlet 18. A new
compression cycle is initiated as previously described.
* * * * *